Broach locking device



April 11, 1939 1. w. FORBES BROACH LOCKING DEVICE 2 Sheets-Sheet l Filed Feb. lO, 1938 ciwm April 11, 1939. .1. w.' FORBES BROACH LOCKING, DEVICE Filed Feb. l0, 1938 2 Sheets-Sheet 2` Patented Apr. 11, 1939 UNITED STATES BROACH LOCKING DEVICE John Walter Forbes, Marlborough, Mass., assignor to The Lapointe Machine Tool Company, Hudson, Mass., a corporation of Maine Application February 10, 1938, Serial No. 189,744

4 Claims.

This invention relates to breaching machines, and more particularly to broaching machines of the vertical type in which the broach is drawn downward through the work by a puller head operating below the work support.

While my improved locking device may be applied to machines in which the broach is manual- 1y returned to raised position above a new piece of work, the invention is exceptionally useful in breaching machines in which the broach is returned to raised position by a mechanical or hydraulic lifter head vwhich is operative after the iinished work has been removed and before a new piece of work has been inserted in the machine.

It is the object of my invention to provide an improved device by which a locking key may be automatically withdrawn from a broach at the lower end of a working stroke, said device being also manually operable to return the key to locking positionrelative to the broach at the beginning of the next working stroke.

My invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of the invention is shown in the drawings, in which Fig. 1 is a side elevation of my improved locking device with the key in locking position;

Fig. 2 is a similar view but with the parts in unlocked position; and

Fig. 3 is a detail sectional view, taken along the line 3-3 in Fig. l.

Referring to the drawings, I have shown portions of a broaching machine including a puller head I l! slidable in guideways Il and having a socket l2 to receive the lower end of a broach B. The broach has a transverse opening or slot I5, as is customary for broaches used in pull-down machines, and the socket I2 is similarly slotted. A key I5 extends through the slots in the broach and socket when the parts are in the position shown in Fig. 1 and securely locks the broach to the puller head. 45 A lever 2i! is pivoted at A.2| in the puller head and is connected to the key I6 by a short link 22. The lower end of vthe lever 20 is connected by an adjustable link 24 to a depending arm 25 of a three-armed lever 26, pivoted in the puller head at 21.

A second arm 28 ofthe three-armed lever 25 is provided with a head 2B adapted to engage a collar 30 which may be adjustably secured on a fixed rod 3l in such position that it will be en- (Cl. S30- 33) gaged by the head 29 as the puller head It! apy proaches its lower limit of travel.

A hand lever 32 is pivoted at 33 on the puller head and its end portion 34 overlies the head 29 and may be used to manually depress the head 29, as will be hereinafter described.

The third arm 3E of the three-armed lever 25 is pivoted at 31 to a yielding toggle link 38 comprising a member 40 containing a compressed coil spring 4| and a telescoping plunger 42 pivoted at 43 on the puller head.

The centers 21, 31 and 43 are so positioned that the toggle link 38 will hold the three-armed lever and associated parts yieldingly in the position shown in Fig. 1 or in the position shown in Fig. 2, and will also complete the movement of said parts in either direction with a snap action as soon as the pivot 31 passes the center line connecting the pivots 21 and 43.

Having described the details of construction of my improved locking device, I will now briey describe the general operation of a vertical pulldown breaching machine having a broach-lifting attachment and adapted to utilize my improvement to the fullest advantage. Such a machine is shown and described in detail in the prior application of Donald H. West, Serial No. 125,871, filed February 15, 1937, and to which reference is made for a more complete and detailed description.

For the purpose of this application, the general operation of the machine may be briey described as follows: When a new piece of work is inserted, the lifter head and broach are in raised position and the puller head is also in raised position but is below the work, while the lower end of the broach is above the work.

The lifter head then moves down, passing the reduced lower end of the broach through the work and seating th same in the puller head. 'Ihe broach is then locked in the puller head, after which the puller and lifter heads and the broach move down together during the broaching stroke.V

Toward the lower end of the stroke. the broach is released from the lifter head and the lifter head stops, while the puller head and broach continue their downward movement untilthe broach is drawn down entirely through the work. The broach is then unlocked from the puller head end but remains seated therein.

After the work is removed, the puller head and broach begin their return upward stroke and the upper end of the broach engages and is locked in the lifter head. Thereafter the lifter head moves up more rapidly than the puller head and withdraws the broach from the puller head to its original position above the work support and above the new piece of work to be inserted.

While said West application discloses mechanism for automatically unlocking the broach from the puller head near the lower end of the working stroke and for locking the broach in the puller head at the beginning of the next working stroke, the device therein shown requires the use of broaches having locking ends of special construction. The West locking device cannot be used with slotted breaches such as have been used generally in the broaching trade for many years and of which many thousands are in use over the country.

The locking device shown in the present application has been specifically devised to permit use of these oldstyle broaches in machines provided with means for automatically raising the broach.

As the puller head ID shown in this application app-roaches the lower end of the working stroke, the head 29 of the lever 26 engages the fixed collar 3U and through its connections withdraws the locking key I6 from the position shown in Fig. 1 to the position shown in Fig. 2, the latter part of the movement taking place with a snap action due to the operation of the yielding toggle link 38.

The parts remain in the position shown in Fig. 2 as the puller head is raised and while the broach is withdrawn and raised above the work support. After the new piece of work is positioned and the broach is again lowered into the socket l2, the handle 32 is pulled upward, thus manually restoring the key I6 to the locking position shown in Fig, 1. It is considered preferable to restore the key manually to avoid possible breakage if the broach is not correctly positioned in the socket for receipt of the key I6.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:

1. In a pull down broaching machine having a puller head, a broach provided with a transverse slot, and a key insertable in said slot to lock said broach in said head, that improvement which consists in providing automatic means to withdraw the key from the slot at the end of the work ing stroke, and manual means to insert the key in the slot at the beginning of the next working stroke.

2. In a pull down broaching machine having a puller head, a broach provided with a transverse slot, and a key insertable in said slot to lock said broach in said head, that improvement which consists in providing a lever connected to said key, a xed stop, and a device engaged by said stop and connected to operate said lever to withdraw said key from the slot as the puller head completes its working stroke, said key, lever and device being mounted on and movable with said puller head.

3. In a pull down broaching machine having a puller head, a broach provided with a transverse slot, and a key insertable in said slot to lock said broach in said head, that improvement which consists in providing a lever connected to said key, a xed stop, a device engaged by said stop and connected to operate said lever to withdraw said key from the slot as the puller head completes its working stroke, and a hand level` by which said key may be manually restored to locking position, said two levers and said device being mounted on and movable with said puller head.

4. In a pull down broaching machine having a puller head, a broach provided with a transverse slot, and a key insertable in said slot to lock said broach in said head, that improvement which consists in providing a lever connected to said key, a xed stop, a device engaged by said stop and connected to operate said lever to withdraw said key as the puller head completes its working stroke, and yielding toggle means effective to complete the withdrawal of said key with a snap action and to hold said key in withdrawn position until said key is manually returned to locking position, said key, lever, device and toggle means being mounted on and movable with said puller head.

JOHN WALTER FORBES. 

